Tobacco consumption patterns among Iranian adults: a national and sub-national update from the STEPS survey 2021

Smoking is recognised as a critical public health priority due to its enormous health and economic consequences. Constant monitoring of the effectiveness of tobacco control programs calls for timely population-based data. This study reports the national and sub-national patterns in tobacco consumption among Iranian adults based on the results from the STEPwise approach to chronic disease risk factor surveillance (STEPS) survey 2021. This study was performed through an analysis of the results of the STEPS survey 2021 which had been conducted as a nationally representative cross-sectional study. Participants included Iranian adults aged ≥ 18 years in all provinces of Iran, who were selected via multistage cluster sampling method. Data were analyzed via survey analysis while considering population weights. The total number of participants was 27,874, including 15,395 (55.23%) women and 12,479 (44.77%) men. The all-ages prevalence of current tobacco smoking was 14.01% overall, 4.44% among women, and 25.88% among men. The all-ages prevalence of current cigarette smoking was 9.33% overall, 0.77% among women, and 19.95% among men. The all-ages prevalence of current hookah smoking was 4.5% overall, 3.64% among women, and 5.56% among men. The mean (SD) number of cigarettes smoked per day was 12.41 (10.27) overall, 7.65 (8.09) among women, and 12.64 (10.31) among men. The mean (SD) monthly times of hookah use was 0.42 (7.87) overall, 2.86 (23.46) among women, and 0.3 (6.2) among men. The national all-ages prevalence of second-hand smoking at home was 24.64% overall, 27.38% among women, and 20.26% among men. The national all-ages prevalence of second-hand smoking at work was 19.49% overall, 17.33% among women, and 22.94% among men. The tobacco consumption in Iran remains alarmingly high, indicating the current tobacco control policy implementation level is ineffective and insufficient. This calls for adopting, implementing, and enforcing comprehensive packages of evidence-based tobacco control policies.

www.nature.com/scientificreports/ The concentration index with Erreygers' correction 10 was used to quantify the degree of inequality in all types of smoking-related to wealth index and years of schooling. A zero concentration index would indicate no inequality related to wealth index or years of schooling. Negative values of concentration index would mean a higher prevalence of smoking among people with lower wealth index or years of schooling. Positive values of concentration index would indicate a higher prevalence of the type of smoking among people with higher wealth index or years of schooling 11 .
Model-based clustering method was applied to the data to achieve homogenous clusters regarding tobacco use on the sub-national level based on the smoking behaviours reported. We used data mining methods to determine the number of clusters and the combination of provinces in each cluster 12,13 .

Results
Sociodemographic status. The total number of participants was 27,874, including 15,395 (55.23%) women and 12,479 (44.77%) men. The sociodemographic status of participants is presented in Table 1.
Geographical pattern of tobacco prevalence. The age-standardised (95% CI) prevalence of all types of smoking varied significantly across the 31 provinces of Iran ( Fig. 2a- Geographical pattern of tobacco prevalence among women. The age-standardised prevalence (95% CI) of ever smoking among women ranged from 0.81% (0. 19-3.35) in Ilam to 20.87% (17.62-24.54) in Sistan and Baluchistan. The prevalence of ever cigarette smoking among women ranged from Zero percent in Ilam, Hormozgan, Sistan and Baluchistan, and South Khorasan to 2.19% (1.19-4) in West Azerbaijan. The prevalence of ever use of hookah among women ranged from 0.23% (0.03-1.59) in Ardabil to 19.5% (16.38-23.06) in Sistan and Baluchistan. The prevalence of current smoking among women ranged from 0.39% (0. 12-1.29) in Chahar Mahaal and Bakhtiari to 16.64% (13.69-20.08) in Sistan and Baluchistan. The prevalence of current cigarette smoking among women ranged from zero percent in Bushehr, Chahar Mahaal and Bakhtiari, Hormozgan, Ilam, North Khorasan Sistan, South Khorasan, Markazi, and Baluchistan to 1.59% (1.04-2.43) in Tehran. The prevalence of the current use of hookah among women ranged from zero percent in Ardabil and West Azerbaijan to 15.27% (12.47-18.56) in Sistan and Baluchistan (Fig. 2b, Supplementary Table 2).
Geographical pattern of tobacco prevalence among men. The age-standardised prevalence (95% CI) of ever smoking among men ranged from 20.94% (16.19-26.65  www.nature.com/scientificreports/ Determinants of tobacco smoking. Wealth and years of schooling. On the national level, lower wealth index or years of schooling were associated with higher prevalence of ever or current tobacco smoking among www.nature.com/scientificreports/ both women and men (Table 3). Nevertheless, wealth index and years of schooling had varying roles in tobacco smoking prevalence among women and men across provinces in Iran (Fig. 6, Supplementary Table 5).
Geographical pattern. Using model-based clustering, the 31 provinces of Iran were categorized into four clusters based on prevalence of ever tobacco smoking, ever cigarette smoking, current tobacco smoking, and current cigarette smoking (Fig. 7). The prevalence of smoking among the four clusters is presented in Table 4.

Discussion
The study showed that 14% of the Iranian adults, 4.4% of women and 25.9% of men, were current tobacco smokers in 2021. Some 9.3% of the study participants, 0.8% of women and 20% of men, were current cigarette smokers. There was a heterogeneous geographical distribution pattern in tobacco smoking prevalence in Iran, distinctively witnessed among the smoking behaviour of women and men, depending on the type of smoking. In northwestern Iran, West Azerbaijan had the second-highest prevalence of current cigarette smoking among men and the fourth-highest among women. Nevertheless, it ranked 16th in terms of current hookah use among men, and the prevalence was nearly zero among women. In southwestern Iran, Bushehr had the highest prevalence of current hookah use among both women and men, while having nearly zero prevalence of current cigarette smoking among women and being ranked as the third-lowest in terms of prevalence among men. In southeastern Iran, women in Sistan and Baluchistan had the second-highest prevalence of current hookah use while having nearly zero prevalence of current cigarette smoking. Sistan and Baluchistan also had the highest prevalence of smokeless tobacco use. The geographical pattern also conformed to neighbouring countries 1,15 , possibly due to ethnic, cultural, and access resemblance 16 .
Using data mining techniques, we grouped Iran's provinces into four clusters with similar prevalence of ever tobacco smoking, ever cigarette smoking, current tobacco smoking, and current cigarette smoking. In provinces in cluster 1, smoking cessation policies need to be prioritized, while other forms of tobacco use, namely hookah are less pressing issues. In cluster 2, which interestingly maps to northwestern Iran, both cigarette smoking and tobacco use need to be addressed. In provinces in cluster 3 both ever/current prevalence of tobacco and cigarette smoking are low. Cluster 4 is consistent with central, southern, and eastern provinces, where tobacco consumption needs to be addressed. The clustering of provinces could empower Iranian authorities in decisionmaking and public policy efforts regarding tobacco control. This needs to be further investigated in future studies which particularly focus on proposing tobacco reduction policies based on the real-world data. Notably, upon www.nature.com/scientificreports/ interpretation of the results of model-based clustering, the role of smoking determinants reported in this study including wealth index and years of schooling need to be considered for policy and intervention development. The prevalence gap between men and women was narrower in the current hookah use compared with current cigarette smoking. The prevalence of hookah use is more than cigarette smoking among women. Moreover, women tend to have more positive attitudes towards hookah use, which is much less stigmatised than cigarette smoking 17 . In recent years, the prevalence of hookah use among women has increased more than men 18 . Alarmingly, the study showed that women's mean monthly times of hookah use was more than nine times that of men. Meanwhile, there is evidence that the deleterious effects of hookah use on women could be higher than in men 19 .
There was an interest in hookah use, particularly among younger adults. Some 19% and 7% of men and women aged 18-24 years had used hookah at least once. Moreover, the prevalence of current hookah use reached a surprisingly early peak of 11% among men and 6% women aged 25-34. Despite supposedly more deleterious effects of hookah use than cigarette smoking 20 , there has been a growing interest in hookah use in recent decades 21 . While hookah use is considered recreational in Iran 16 , there is evidence that hookah users are increasingly susceptible to cigarette smoking 22,23 .
Six decades after the first documentations of the deleterious health effects of tobacco use 24 , there has been substantial progress in reducing the prevalence of tobacco smoking worldwide. In contrast, it is estimated that the age-standardised prevalence of current tobacco smoking has increased by 8% among men and 2% among women in the past three decades in Iran and the population growth has also led to a marked increase in the number of smokers 1 . Since introducing the WHO Framework Convention on Tobacco Control (FCTC) in 2005, outlining demand-reduction policies, many counties have witnessed drastic decreases in the prevalence  Though once an early adapter to FCTC 16 , the current tobacco control policy implementation level is insufficient in Iran. In the absence of any new concerted effort towards smoking reduction, sanctions and subsequently the economic downturn could have played a significant role in the slight reduction of smoking prevalence in Iran since 2016 14,16,27 . Evidence shows that economic recessions are associated with decreased cigarette consumption via decreasing its affordability 16 . Overall, cigarettes have become less affordable in Iran, particularly since 2018 28 . The purchase pattern of Iranian smokers has changed from the whole box of cigarettes to the single stick cigarette. In addition, smokers have generally swapped to less expensive cigarettes 29 . Dealing with the burden attributable to tobacco use, public health authorities encounter substantial obstacles such as an increased number of smokers due to population growth, pressure from the tobacco industry, and competing for health and political priorities 1 . WHO discourages Iran from implementing high import duties as they encourage domestic production of tobacco. Direct taxation also needs to be excised rather than other indirect taxes.
Moreover, uniform tax rates are recommended to avoid product switching 28 . There is evidence that tobacco taxation, as one of the most cost-effective tobacco control policies 30 , needs to be concordantly adjusted to people's purchasing power to remain potent and reduce affordability 31 . Moreover, the revenue from tobacco taxation needs to be redistributed to tobacco control programs, health care services, and social support services 30 . Unless strict regulations are in place to control cigarette smuggling, any increase in cigarette price could be compensated by flooding smuggled cigarettes into the market 29 . This calls for substantially reducing smoking rates in the country via adopting, implementing, and enforcing comprehensive packages of evidence-based tobacco control policies. The witnessed heterogeneities and determinants in the patterns of smoking prevalence and tobacco consumption need to be taken into account when prioritizing vulnerable groups and designing tobacco reduction strategies, especially considering the relative authority of the medical universities of Iran in sub-national healthcare programs implementation 32 . Otherwise, the death toll, imposed economic costs, and the burden to health systems caused by smoking will increase over the years.

Strengths and limitations.
The main strength of this study lies in its large sample size. Given the sampling method, the results could represent the Iranian population. The study investigated the smoking prevalence and tobacco consumption pattern by age, sex, province of residence, wealth, and years of schooling. This could empower public health authorities to make evidence-based decisions and design tobacco reduction action plans based on various determinants according to real-world data, especially considering that individual level data were used for assessing the inequality patterns. Moreover, this was the first nationwide study from Iran to investigate pipe smoking and the use of smokeless tobacco. Given the use of electronic and online data gathering tools, the study had very little missing data. To minimise the missing data, the software used for data collection was designed to avoid ignoring obligatory questions. Moreover, the estimated sample size was initially calculated to be 10% higher than the required sample size so that potential missing data did not violate the sample representativeness. Table 3. Concentration index for wealth and years of schooling for tobacco and cigarette smoking among women and men. www.nature.com/scientificreports/

Conclusion
The tobacco consumption in Iran remains alarmingly high, indicating the current tobacco control policy implementation level is insufficient. This calls for adopting, implementing, and enforcing comprehensive packages of evidence-based tobacco control policies. In the meantime, the witnessed heterogeneities in the patterns of smoking prevalence and tobacco consumption need to be considered when designing tobacco reduction strategies. Otherwise, the death toll, imposed economic costs, and the burden to health systems caused by smoking will increase over the years. www.nature.com/scientificreports/

Data availability
The datasets used and analysed during the current study available from the corresponding author on reasonable request.  www.nature.com/scientificreports/ Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/.